Just a few blocks from the U.S. Capitol in Washington, DC, begins a swath of riverfront green space about 1.5 times the size of Central Park. Here, a short walk from homes that sell for more than half a million dollars each, geese outnumber people. The river is quiet, with scarcely a boat in sight. On a clear day, a visitor can see into the windows of the gleaming new condos rising on the other shore.

Anacostia Park was supposed to be an urban oasis, a city escape that would feature a swimming lake, Tivoli-style gardens, pleasure boating and fishing. Yet, nearly 100 years after the federal government established it on the city’s northeast side, Anacostia Park remains a place yet to reach its potential.

Yes, it has a roller rink, the only one in a national park. Thousands of visitors came on a recent spring weekend for the second annual Anacostia River Festival, which now marks the end of the city’s traditional four-week celebration of its cherry trees blossoming.

But the goalposts on the soccer fields in one portion of the park are rusting. Silt fences encircle a playground, making it an uninviting and muddy mess. The whole park includes only one spot with picnic tables, and it lacks shade. Perhaps that explains why, on a 60-degree day, almost no one is enjoying the vast, linear expanse that, on paper at least, was to give DC “a park of great beauty and value,” according to the federal Commission of Fine Arts.

“Think of what we could do with this,” Doug Siglin said as he stretched his arms toward the Anacostia River on one side and the flat, green lawn on the other. “This is a national park, in the nation’s capital, and nothing, nothing, nothing, is happening here.”

Siglin is the latest in a long line of planners, architects, city leaders and river advocates to try to make something happen at Anacostia Park. As executive director of the Anacostia Waterfront Trust, the longtime environmental lobbyist has been researching past plans for the park and trying to pull together a vision for its future.

It’s a tricky balance in the quickly gentrifying District of Columbia. Its population has grown close to 700,000 people since the 1990s, and is expected to reach a million in the next 20 years. To house the newcomers, new housing stock has pushed into neighborhoods east of the Capitol, many of which had been historically African American and lower middle class.

That gentrification is coming ever closer to the Anacostia’s banks. Already, a new baseball stadium for the Washington Nationals has changed the skyline. The river is cleaner than it has been in decades, and the local governments that share responsibility for the watershed have plans to clean it more.

Washingtonians used to laugh when Jim Foster, president of the Anacostia Watershed Society, would tell them that the river would be swimmable and fishable by 2020. Now, he contends, it’s more of a quiet snicker — even if most residents acknowledge such a swift improvement for such an abused river is unlikely. The district and federal government, as well as the neighboring counties, Montgomery and Prince George’s, have already invested or are planning to spend several billion dollars cumulatively to curtail sewage overflows, reduce runoff pollution and upgrade wastewater treatment plants.

Despite those efforts, the Anacostia is still riddled with toxic contaminants in the sediment. The industrial legacy of energy facilities and military installations that lined its banks contributed so much pollution that remediating it all will require years and cost billions of dollars.

Some of the neighborhoods around the river also remain depressed.

“My biggest challenge really,” Foster said, “is changing the frame of reference people have about the Anacostia.”

Longtime Anacostia resident Arrington Dixon has been trying for more than two decades to bring more investment to Anacostia Park. He’d like to see job-training programs in landscape architecture, more places for boating and a winter ice rink. Dixon, president of his own technology firm and former chair of the DC City Council, now leads the Anacostia Coordinating Council, a local nonprofit trying to make improvements.

Time and again, Dixon said, the Anacostia neighborhoods get overlooked, a function of the poverty and transience of many of its residents. They lack the political connections to make things happen.

“If you’re not at the table, you’re on the menu,” Dixon said. “And we’re on the menu right now.”

In many ways, the Anacostia’s misfortunes date back to the District’s founding as the nation’s capital. Though George Washington and Thomas Jefferson envisioned the river as part of a new and grand federal city, things turned out differently when the street grid got laid out. District architect Pierre L’Enfant designed the city to be on the west side of the Anacostia only.

Thus, the Potomac became the nation’s river, and the Anacostia was relegated to a backwater that housed the inmates of St. Elizabeth’s Asylum and troops at various military installations.

As the settlement on the Potomac prospered, the Anacostia and the land around it languished. In 1900, the Board of Trade called it an “uninviting river” with “miasmatic swamps, whose baneful influence is so seriously felt by a large portion of the citizens of Washington.”

A park, city leaders reasoned, would make the city and the river more inviting, according to a paper Siglin wrote for the Smithsonian.

Celebrated urban architect Frederick Law Olmsted Jr. worked on plans for the park in 1900. Little had happened, though, and 67 years later, Lady Bird Johnson took up the cause and formed a committee urging improvements to the park be completed in the next decade.

Instead, Washington’s vast transportation network cut the park into pieces. Interstate 295 crosses the park, as does a railroad and the river itself. Stretching from Kenilworth Aquatic Gardens and the National Arboretum down to the Nationals baseball stadium, the Anacostia Park is broken into sections, some named, some simply identified as “Section D” or “F.”

What often holds the District back, Dixon said, is its lack of political power. The city, which lacks a vote in Congress, often doesn’t control its own destiny.

A case in point: About 190 acres of Anacostia park is a paved parking at the nearly defunct RFK Stadium. The District would like to rip up the lot; but the land is leased to the stadium, for 20 more years and, in any case, officially belongs to the National Park Service. Transferring ownership to the District would take an act of Congress, something Siglin fears is unlikely

In the meantime, the veteran Capitol Hill lobbyist is working with the nonprofit Federal City Council on a vision for Anacostia Park. Siglin’s vision incorporates many of the amenities Dixon has pushed: more usable green space, trees, an environmental center and job training opportunities. The investment along the river — or its more affluent west side anyway — is transforming the area. A new soccer stadium is coming. Condo buildings surround the Capitol dome. Two decades ago, none of it was here; two decades from now, it will look different still.

“We need to spread the wealth, but we need to bring it over here in a way that is not going to drive people away,” Siglin said. “Has that been successfully done anywhere? I don’t think so. There aren’t any models. So we have an opportunity to make this up and do it right.”

Anacostia Park is starting to get increased attention, as federal park and wildlife agencies invest in more urban sites and programs. An executive order from President Barack Obama’s also focused attention on the river, and the Chesapeake Bay’s Total Maximum Daily Load is helping to drive the cleanup, especially for stormwater.

In addition to hosting the Anacostia festival, the National Park Service partnered with 25 nonprofit groups to ensure good attendance by providing a shuttle bus and bicycle valet services. NPS spokesperson Emily Linroth said the agency is “absolutely committed” to improving the park.

“It’s critical to make sure people can get to these places and that they resonate with them,” Linroth said. “A lot of people have this national park in their backyard. Some know it and love it, and some have no idea.”